The invention relates to a process for producing oxacarbonylated polymers by opening rings and polymerization of monomers comprising at least one cyclic oxacarbonyl function, such as a lactone function.
Lactones have a known capacity to polymerize, under reaction conditions and according to mechanisms which vary essentially depending on the starting lactone monomer and on the catalyst or initiator used. In order to initiate polymerization by opening rings, the prior art teaches a diversity of initiators; thus, the latter may be anionic in nature, such as a hydride, a carbanion, an alkoxide, a thiolate or an alkali metal, alkaline earth metal, aluminum, zinc or tin carboxylate; it may be nucleophilic and uncharged in nature, such as a tertiary amine for polymerization of xcex2-propiolactone, or a phosphine; it may also be chosen from protic compounds such as carboxylic acids, alcohols, glycols, or polar functions such as primary and secondary amines and combinations of structures such as alkanolamines, or from coordination complexes, such as those of aluminum.
In general, the polymerization reaction is carried out in totally anhydrous medium, in an inert solvent, at a temperature which must sometimes exceed 150xc2x0 C.
Polymerization conditions known to date produce, however, great variability of polymerization yields and of the polymolecularity and polydispersity indices for the polymer obtained, depending on the starting monomer. In addition, the known initiators are often undesirable and/or toxic.
The present invention provides a process for producing oxacarbonylated polymers from monomers comprising at least one cyclic oxacarbonyl function, and in particular a lactone function, making it possible, under gentle reaction conditions, to obtain complete consumption of the starting monomer(s).
Specifically, according to the process of the invention, firstly, a temperature close to room temperature is often sufficient to polymerize certain lactones, for which the reaction requires high temperatures using known polymerization processes, and, secondly, polymers which, after washing, are free of starting monomers and of initiator are produced, which makes them very easy to isolate and makes it possible to envision using them in very varied applications, including those in which it is essential to have a pure polymer.
The process of the invention comprises the following steps:
At least a monomer comprising at least one cyclic oxacarbonyl function, and an initiator, are available,
The polymerization or copolymerization of said monomer is carried out in bulk or in solution,
The initiator being chosen from the bicyclic guanidine compounds corresponding to formula (I) or formula (II) 
in which one and/or the other of the rings may be substituted, in at least any one of positions 2, 3, 4, 8, 9 and 10 of formula (I) or in at least any one of positions 2, 3, 7 and 8 of formula (II), with at least one radical chosen from alkyl groups having from 1 to 6 carbon atoms, cycloalkyl groups having from 5 to 7 carbon atoms and the hydrocarbon-based chains of polystyrene.
An oxacarbonyl function is intended to mean a function xe2x80x94Oxe2x80x94COxe2x80x94 included in a ring, the monomer therefore comprising at least one oxygenated heterocycle. By way of example, it may be a lactone function.
A preferred initiator corresponds to formula (I) and is 7H-1,5,7-triazabicyclo[4.4.0]dec-5-ene (hereinafter denoted TBD).
As mentioned above, the monomer(s) may comprise at least one lactone function; they are then advantageously chosen from the group consisting of xcex5-caprolactone, xcex4-valerolactone, xcex2-butyrolactone, xcex3-butyrolactone, 2,6-dimethyl-1,4-dioxan-2,5-dione (or lactide) and 1,4-dioxan-2,5-dione (or glycolide).
Depending on the choice of starting monomer(s), the process leads to the production of a homopolymer if only one monomer is available, or of a copolymer, the latter possibly being a block copolymer or a random copolymer, if at least two different monomers are reacted.
The preferential reaction conditions of the process according to the invention are stated hereinafter, and they should be considered alone or in combination:
the molar ratio of the monomer(s) to the initiator ranges from 1 to 500, advantageously from 1 to 200,
the reaction is carried out at a temperature ranging from 0xc2x0 C. to 150xc2x0 C., preferably from 50xc2x0 C. to 120xc2x0 C.,
the reaction is carried out in bulk; it may also be carried out in a solvent, in particular chosen from tetrahydrofuran (THF), toluene, acetone and dibutyl ether,
the reaction duration ranges from 10 minutes to 12 hours.
A subject of the present invention is an oxacarbonylated polymer which can be produced using the production process defined above.
The process of the invention also has the advantage of making it possible to functionalize the polymers obtained in situ, directly in the reaction mixture, so as to produce activated or activatable polymers modified by functionalization. This functionalization is carried out using a functionalizing agent and, depending on the intended purpose of the polymer, this functionalization may be particularly advantageous. By way of illustration, after functionalization, biodegradable modified polylactones are produced, having the properties of an agent which modifies the viscosity of organic solvents and aqueous media, including water.
A functionalizing agent according to the invention is preferably a linear or branched molecule or macromolecule comprising at least one alcohol or amine function.
This agent may be selected from:
pure functionalizing compounds, such as butanol, ethoxyethanol, pentraerythritol, allylamine, methoxyethylamine, decylamine, ethoxyethanolamine and esters of carboxylic acids,
functionalized polymers, for instance polymers and copolymers, such as polymers and copolymers of alkylene glycol, and especially polymers and copolymers of ethylene glycol, in particular copolymers of ethylene glycol (PEG) and of propylene glycol (PPG), mixtures of said polymers, mixtures of said copolymers, mixtures of said polymers and copolymers, polyalkyleneamines such as Jeffamines(copyright), polyesters such as polyethylene terephthalates, and mixtures thereof,
with natural products such as polyglucosides and, by way of example, gums, dextrans, chitosans and starch, and from mixtures of these agents, and
mixtures of the abovementioned agents: by way of example, the mixture comprising at least one ethylene glycol polymer and at least one polyglucoside may be chosen.
Gums, such as xanthan gum and guar gum, optionally mixed with another functionalizing agent, such as an alkylene glycol polymer, constitute particularly advantageous agents.
The polymerization and the functionalization may be carried out sequentially or they may be carried out in situ simultaneously, in bulk or in the solvent.
Thus, the invention relates to a process for producing oxacarbonylated polymers, as defined above, according to which a functionalizing agent is added to the monomer and to the initiator, according to an in situ method or a sequenced method. A preferred agent is chosen from the agents listed above.
A subject of the invention is also an agent for functionalizing an oxacarbonylated polymer, which comprises at least one gum, such as a xantham or guar gum, combined with at least one polymer and/or one copolymer of alkylene glycol oxide, such as the polymers and copolymers of ethylene glycol oxide (PEG).
The invention also relates to a functionalized oxacarbonylated polymer which can be produced using the polymerization a nd functionalization process defined above.
Another subject of the invention is the use of a bicyclic guanidine compound corresponding to formula (I) or (II) mentioned and described above, for initiating the reaction of polymerization or of copolymerization with the action of monomers comprising at least one cyclic oxacarbonylated function. Advantageously, the bicyclic guanidine compound is TBD.
According to a variant of use of the initiator of the invention, the latter is attached directly or indirectly, or deposited, onto a solid support. By way of example, a suitable support is mineral or organic and consists of a resin, a polymer such as a polystyrene or a polypropylene, a copolymer such as a polystyrene/divinylbenzene copolymer, silica, clay, diatomite, zeolite, alumina or aluminosilicate. The expression xe2x80x9cdirectly or indirectlyxe2x80x9d is intended to mean that said agent comprises, at least on one of its rings, a radical capable of binding to said support, or a radical which will be bound to said support via a coupling arm. The latter is generally a hydrocarbon-based chain. The term xe2x80x9cdepositedxe2x80x9d is intended to mean that said initiator is adsorbed onto an organic or mineral support.